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Just my take on this but as far as the tension bolts go, I would never safty wire them.
Between the rubber sealing washers used on these and the very long spring tension on them (when properly torqued) I don't think it is possible for them to vibrate loose. This self retention on tension bolts is so extream that impact wrenches will usually not remove them. The bolts just spring back to original position after each impact. You have to break them loose with a hand wrench first.
If a tension bolt comes loose while in use, it probably was not tightened properly in the first place.
Tracy (back from Osh)
On Mon, Jul 28, 2008 at 5:16 PM, Ed Anderson <eanderson@carolina.rr.com> wrote:
Yeah, I've never measure the angle so who really knows. Gee, that takes some precision drilling there, Bill. Now, we'll all know where to send our tension bolts to be drilled {:>).
Actually, I use a racers trick for retention of the long rotary tension bolts. A couple of folks have actually had one back out in flight. Fortunately, the one incident I am familiar with was using the heavy fly wheel (rather than the flex plate although I don't know whether it would have made a difference) and when the bolt came loose and backed its head out into the path of the flywheel something caught the bolt and bent a 90 deg bend in it. Fortunately, the rotary got the aviator back safely, but suffice it to say one does not want tension bolts backing out like that.
I notice on one of the junk 13Bs I acquired that had been used by a racer, that there was a thin steel sheet disc that was bolted using the outer seal bolts but which extend out almost the full diameter of the block covering the heads of all the tension bolts. Needless to say, that precludes any backing out into the fly wheel/flex plate. But, does not keep them from coming loose like a safety wire would.
Yes, I use the metal lock nuts (NOT the ones with plastic inserts for any new comers to aviation) for all bolts in the engine compartment including my prop.
Now back to programming.
Ed what's a couple of degrees between friends? Al suggested he has used metal lock nuts whenever possible. I like this solution. the steel Jet-nuts are fantastic if somewhat expensive. With reguards to weakening bolts by wiring, I will use a technique where I drill through a corner only on low-grade nuts or bolts. This is a little tedious but I've done 30 in an hour when I did them production style. First I spot the bolt with a slightly larger drill, them I drill perpendicular to the cone surface a short distance with a .06 drill. This sounds hard but if you hold the head by the flats it lines up perfectly. Then do the same thing on an adjoining flat. Not as good as the AN through drilled bolt, but easy to do. Works on nuts too! I've done this on exhaust nuts on a problem engine I had. Not the only solution, and sometimes overkill. The biggest advantage of having bolts drilled for wire is that you will usually tighten them before wiring them! This is the reason racers use a lot of wire. the wire is a great reminder when replacing parts. If I have anything on my plane that I find I'm removing and replacing a lot it WILL be safety wired. Most items DON'T NEED safety wire, if you remember to tighten them.
Bill Jepson
-----Original Message-----
From: Ed Anderson <eanderson@carolina.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, 28 Jul 2008 9:46 am
Subject: [FlyRotary] Re: Safety wire
That's impressive, Bill. I don't think (as Lynn said) and aircraft ever came out of the sky because of safety wire but plenty have because lack of it. However, some bolts and such on the rotary, you would need to drill the heads/nuts yourself in that case, I'm think I would look to other alternatives as drilling a bolt head or threaded part could weaken it. Fortunately, the vibration level is lot lower on the rotary compared to most reciprocating engines.
By the way, I'll bet you even wire the 37 deg AN fittings as well {:>)
Rv-6A N494BW Rotary Powered
Keith,
there will be many divergent opinions on this I'm sure. My personal mantra is safety wire anything you don't want to fall off! There are several approaches too. I am an ex motorcycle racer and the rules required all basic safety items to be wired. Those were, all oil drains, water drain plugs if any, brake mount bolts, and oil feed bolts and filters. I would usually do more than was required. I have seen many things vibrate off that you wouldn't think possible when operating at high power levels. I would use both .039 and .025 stainless steel safety wire. The .025 isn't FAA approved on a lot of things, but it's light and serves the purpose. I even wired 39°AN fittings, which isn't required.
Bill Jepson
-----Original Message-----
From: ktradcliff@comcast.net< /A>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sun, 27 Jul 2008 5:07 pm
Subject: [FlyRotary] Safety wire
Hello everyone,
I know that the subject of safety wire has been discussed many times before,
however searching the archives can at times be very difficult and actually
finding the answer you want is like winning the lottery (it never happens).
What I would like to know is what most are considering an absolute must to be
safety wired. What the FAA r
equires and what is not so important but some are
doing anyway. I feel that the subject of safety can never be discussed enough.
I would like everyone that has an opinion on safety wire and what must be safety
wired to weigh in on this subject. I plan to save some if not all of your
answers for future reference. Maybe we can make a list of what must be safety
wired.
Thanks
Keith
RV-7A
13-B
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